What version of GSSDP and GUPNP are you using? I was having a similar discovery problem, but just upgraded to the latest release tarballs to try some of the discovery fixes, and that resolved everything for me.
When upgrading my F24 from gupnp-0.20.17 & gssdp-0.14.15 to 0.20.18 & 0.14.16 things are working just fine now using just port 40000 udp/tcp + 1900/udp. I've restarted it a couple of times after reaching 30 minutes without losing devices + have been run fine now for 5h.